This project is designed to encourage communication and cooperation among the institutions in the investigation of the role of intraoperative radiotherapy for the treatment of intra-abdominal malignancies. The project is also designed to encourage cooperation in a coordinated program to evaluate the use of radiation modifiers in conjunction with intraoperative radiotherapy. The ultimate goal is to develop guidelines for Phase II and randomized Phase III studies to evaluate intraoperative radiotherapy, alone or with radiation modifiers, for the treatment of intra-abdominal malignancies initially and later in other sites.